Nitridogermanate

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The nitridogermanates are chemical compounds containing germanium atoms bound to nitrogen. The simplest anion is GeN48−, but these are often condensed, with the elimination of nitrogen.

Nitridogermanates can form quite a few structures. Germanium can be in three different oxidation states. In the +2 oxidation state there is [GeIIN2]4− which has a boomerang shape. The most common is the +4 state with [GeIVN3]5− is a planar three pointed star, and [GeIVN4]8− as tetrahedra. Condensation of the tetrahedra yields [Ge2 IVN6]10−. The +3 state is rare, and represented by [GeIII 2N6]12− with a covalent bond between the two germanium atoms.[1] A few compounds also contain germanium in negative oxidation states −2 and −4 and so can be considered germanides as well.

Synthesis

Reduced compounds may be produced by using a flux of molten sodium. Nitrogen may be introduced by using sodium azide. Alkaline earth elements increase the solubility of nitrogen in molten sodium. Containers can be made from sealed tubes of niobium or tantalum. The sodium can be evaporated by heating to over 300°C in a vacuum.[2]

Properties

Nitridogermanates tend to be unstable in air, as they react with water vapour to form ammonia.

Related

Nitridogermanates are in the category of nitridotetralates, or more generally nitridometallates, tetrel pnictides or pnictidometallates. Related compounds include the nitridosilicates, and rare nitridostannates. By varying the pnictogen, there are also the phosphidogermanates. Other similar compounds are the nitridogallates and nitridomanganates.

Subtypes may be termed nitridoalumogermanates or nitridomagnesogermanates, if they contain aluminium or magnesium.

List

name formula formula

weight

crystal

system

space

group

unit cell Å volume density comments ref
α-Ge3N4
phenacite phase of germanium nitride β-Ge3N4
spinel germanium nitride γ-Ge3N4 Fd3m a 8.2125Å b 8.2125Å c 8.2125 [3]
Ca2GeN2 tetragonal P42/mbc a = 11.2004, c = 5.0482, Z = 8 black [2][4]
Ca4GeN4 monoclinic P21/c a = 9.2823, b = 6.0429, c = 11.1612, β = 116.498°, Z = 4 orange [2]
pentacalcium nitridodigermanate Ca5[Ge2N6] C2/c a 9.836 b 6.0519 c 12.757 β 100.2° colourless [5][6]
Ca6[Ge2N6] trigonal R3 a=9.2078 c=9.2679 680.5 3.439 grey; band gap 1.1 eV [1]
Ca7[GeN6] orthorhombic Pbcn a = 10.826, b = 6.194, c = 13.121 Z=4 879.8 3.301 yellow with N3− [7]
Ca0.8Li0.2Al0.8Ge1.2N3 a = 9.9822, b = 5.7763, c = 5.1484, Z = 4 [8]
Li4Ca13Ge6N18 monoclinic C2/c a = 12.328 b = 12.662 c = 14.711 β = 108.688° 2175.2 3.776 clear [9]
Mg5Ca2GeN6 P63/mmc a = 3.453, c = 17.51 180.8 [2][10]
Mg5Ca4Ge3N10 monoclinic C2/m a = 11.269, b = 3.327, c = 8.008, β = 109.80° Z=4 282.4 colourless; layered [2][11]
ZnGeN2
strontium gallium germanium subnitirde Sr2GeGaN monoclinic P21/c a=6.885 b=4.0432 c=8.680 β =108.454 Z=2 229.21 4.804 black glossy [12]
Li3Ca4(Ga3Ge)N8 [13]
α-Sr2[GeN2] 275.85 tetragonal P42/mbc a=11.773 c=5.409 Z=8 749.7 black [1][14]
β-Sr2[GeN2] 275.85 orthorhombic Cmac a=5.441 b=11.377 c=12.229 Z=8 756.9 4.841 black with blue sheen [14][15]
Sr3Ge2N2 436.1 monoclinic P21/m a = 9.032, b = 3.883, c = 9.648, β = 112.42°, Z=2 312.9 4.630 dark blue-grey [16]
Sr4[GeN4] monoclinic P21/c a = 9.7923, b = 6.3990, c = 11.6924 β = 115.966° dark red [17]
Sr5[Ge2N6] 667.36 monoclinic C2/c a = 10.408, b = 6.521, c = 13.565, β = 100.29° Z = 4 905.8 4.893 yellow/ orange [1][5]
Sr7[GeN6] orthorhombic Pbcn a = 11.526, b = 6.587, c = 13.836 Z=4 1050.5 4.869 red with N3−; Sr in 4-fold coordination [1][7]
Sr6[Ge2N6] trigonal R3 a=9.6655 c=9.6655 790.91 4.755 black; band gap 0.2 eV [1]
Sr8Ge2[GeN4] monoclinic Cc a = 10.1117, b = 17.1073, c = 10.0473, β = 115.966° black [17]
pentastrontium nitridodigermanate Sr6Ge5N2 916.69 orthorhombic Pmmn a = 4.0007, b = 17.954, c = 9.089 Z=2 652.8 4.663 black; unstable in air [18]
Strontium Germanium Nitride Sr11Ge4N6 1338.24 tetragonal P4nbm a=7.278 c=18.681 Z=2 989.5 4.491 black; contains Ge4− [19]
Sr17Ge6N14 triclinic P1 a = 7.5392, b = 9.7502, c = 11.6761, α = 103.308°, β = 94.651°, γ = 110.248° black; contains Ge4− [17]
Li4Sr3Ge2N6 monoclinic C2/m a=6.1398, b=10.021, c=6.3130, β=91.279°, Z=2 [20]
Mg3SrGeN4 tetragonal I4/m a = 8.316, c = 3.398, Z = 2 [2][21]
MgSr3GeN4 orthorhombic Pnna a=5.939, b=10.320, c=9.618, Z=6 yellow [2][22][15]
Ba3Ge2N2 monoclinic P21/m a = 9.61196, b = 4.0466, c = 10.1337 β = 113.55° Z=2 361.61 5.375 metallic; contains Ge2− [23]
Ba6Ge5N2 1215.01 orthorhombic Pmmn a = 4.1620, b = 18.841, c = 9.6116 Z=2 753.7 5.354 black; unstable in air [18]
Ba9Ge3N10 rhombohedral R3c a=7.9399 c=17.282 Z=2 943.53 5.610 black [24]
MgBa3GeN4 orthorhombic Pnma a=6.159 b=10.558 c=10.048 Z=4 653.4 5.743 yellow [2][25]
Mg3BaGeN4 tetragonal I4/m a = 8.392, c = 3.4813, Z = 2 [26]
barium gallium germanium subnitirde Ba2GeGaN monoclinic P21/c a 7.249 b 4.21 c 9.314 β 108.87° black glossy [27]

References

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